Doors and methods of producing same

ABSTRACT

One aspect of the present invention is directed to a door, and more specifically, to a door that includes a web and a rigid foamed core. In one embodiment, a door is disclosed which comprises a door shell having a generally planar construction with marginal edges and first and second door skins helping to define an interior door cavity, a web disposed within the interior door cavity, and a rigid foamed cementitious core disposed within the interior door cavity and cooperating with the web.

CROSS-REFERENCE TO A RELATED APPLICATION

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/131,056, filed Apr. 24, 2002, entitled “HighPerformance Door”, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] One aspect of the present invention is directed to a door, andmore specifically, to a door that includes a web and a rigid foamedcore.

[0004] 2. Background Art

[0005] Door systems have been designed to pass security tests, such asBritish standard PAS 23 (PAS 23), British standard PAS 24 (PAS 24), andFlorida Building Code Test TAS/PA 201 (TAS/PA 201). These door systemsare customarily designed to prevent forcible entry by tools as definedby PAS 23 and PAS 24 and to pass an impact test simulating large missiledebris impact during high velocity wind storms, such as hurricanes ortyphoons, as defined by TAS/PA 201.

[0006] Many steel doors pass some security tests. However, these doorsare less desirable as entry way doors since they lack aesthetic detail,rust and dent readily. For example, entry way doors to common areas inapartment complexes and hotels experience significant use and receivesubstantial physical abuse, lending to significant rusting and denting.By way of another example, entry way doors along salt water coastsreceive substantial physical abuse and are susceptible to corrosivechemical attack.

[0007] Other doors are particularly successful in resisting rust anddenting. For example, fiberglass reinforced plastic (FRP) doors, glassreinforced plastic (GRP) doors, simple fiberglass doors, thermoplasticdoors (such as PVC doors, poly-carbonate-skinned doors), andacrylic-capped acrylonitrile butadiene styrene (ABS) skinned doorscommonly have this positive attribute. This success can be partiallyattributed to minimizing the effects of rusting and denting whileoffering an aesthetically pleasing appearance at a reasonable price.

[0008] However, these doors have had difficulty meeting the requirementsof PAS 23 and PAS 24. For example, the plastic on these doors can be cutwith tools, such as utility knives and wrecking bars. These doors havedifficulty absorbing the impact of a nine pound 2″×4″ piece of woodtraveling at approximately 35 miles per hour, as required by TAS/PA 201.These results are unacceptable to certain customers, particularly publichousing officials who control specifications for apartments in theUnited Kingdom and to building code officials in high velocity wind zoneareas, such as Florida in the United States.

[0009] In light of the disadvantages inherent in the doors available inthe market place, it would be desirable to provide a door thatsuccessfully passes PAS 23, PAS 24 and/or TAS/PA 201 tests. Moreover, itwould be desirable to provide a door that resists denting and rustingand is reasonably priced through reduced material costs. Additionally,it would be desirable to provide a door that is a positive pressure firerated door and/or retards sound transmission.

SUMMARY OF THE INVENTION

[0010] According to one aspect of the present invention, doors areprovided that can be used as security doors that can pass PAS 23, PAS24, and/or TAS/PA 201 tests.

[0011] An aspect of the present invention provides doors that resistdenting and are reasonably priced.

[0012] Another aspect of the present invention provides doors that arepositive pressure rated doors.

[0013] Yet another aspect of the present invention provides doors thatretard sound transmission.

[0014] In certain embodiments of the present invention, a doorcomprising a door shell having a generally planar construction withmarginal edges and first and second door skins helping to define aninterior door cavity, a mat within the interior door cavity, and a rigidfoamed cementitious core within the interior door cavity is disclosed.In certain embodiments, the mat includes openings, for example, a web.Examples of materials suitable for the mat, include, but are not limitedto a substantially rectangular plastic bladder filled with gas, or aballastic resistant material. The door shell can be comprised of ablow-molded material, for example, a pre-pigmented plastic, athermoformed material or a twin-sheet thermoformed material. The doorskins can be comprised of, for example, fiberglass or a thermoplasticmaterial.

[0015] The rigid foamed cementitious core can cooperate with the mat. Inone embodiment, the rigid foamed cementitious core is comprised of afoamed cement slurry. The rigid foamed cementitious core can be disposedbetween the first and second door skins and on at least one side of theweb. Alternatively, the core can be disposed on both sides of the web.The web can be offset towards one of the door skins or substantiallycentered in the interior door cavity. The web can be comprised of manydifferent materials, for example, metal screen, polymer woven sheet, orexpanded metal mesh.

[0016] In certain embodiments, the door can further comprise an adhesivelayer partially coating the internal surface of at least one door skinfor at least partially adhering the rigid foamed cementitious core tothe at least one door skin. Examples of suitable adhesives include, butare not limited to, latex acrylic, hot melt urethane, epoxy, pressuresensitive adhesives, and radiation cured adhesives.

[0017] In certain embodiments, the rigid foamed cementitious coreprevents the passage of fire for at least about 20 minutes using testmethod ASTM E2074-00 or at least about 30 minutes using test method BSI476/22. In other embodiments, the rigid foamed cementitious coreprevents the passage of fire for at least 45 minutes using test methodASTM E2074-00 or at least about 60 minutes using test method BSI 476/22.In yet other embodiments, the foamed cementitious can provide a soundtransmission coefficient rating of at least about 27 using test methodASTM E-413. The foamed cementitious core can also have a compressivestrength of at least about 210 kPa.

[0018] Another aspect of the above-mentioned door includes a door shellhaving a door frame having first and second rails and first and secondstiles. In those embodiments with an expanded metal mesh web, the meshcan include apertures having a first dimension longer than a seconddimension. In certain embodiments, the first dimension can besubstantially parallel to the first and second stiles. It should beunderstood that more than one web can be disposed within the interiordoor cavity.

[0019] In another embodiment of the present invention, a door comprisinga door frame and at least one door skin being connected in helping todefine an interior door cavity, a mat within the interior door cavity,and a rigid foamed cementitious core within the interior door cavity isdisclosed.

[0020] Another embodiment of the present invention is a method ofconstructing a door. The method comprises providing a door shell havinga generally planar construction with marginal edges and first and seconddoor skins helping to define an interior door cavity, disposing a matwithin the interior door cavity, and disposing a rigid foamedcementitious core within the interior door cavity. In certainembodiments, the mat can include opening, for example, a web. In someembodiments, the rigid foamed cementitious core cooperates with the web.In certain embodiments, the web is disposed within the interior doorcavity prior to disposing the rigid foamed cementitious core within theinterior door cavity. The web can be disposed offset toward one of thedoor skins or substantially centered in the interior door cavity. Theweb can be secured to at least one of the door skins or alternatively tothe marginal edges of the door shell.

[0021] In another embodiment, the method further comprises forming ashelf into the marginal edges of the door shell. The forming step can becomprised of removing a portion of the marginal edges such that a firstand second shelf surface is formed into the marginal edges. In certainembodiments, the first shelf surface is substantially parallel to thefirst and second door skins and the second shelf surface issubstantially perpendicular to the first and second door skins. Incertain embodiments, at least a portion of the web can be secured to atleast a portion of the first shelf surface. The first shelf surface canbe offset toward one of the door skins or substantially centered betweenthe first and second door skins.

[0022] In yet another embodiment of the present invention, a door isprovided that comprises a door shell having generally planarconstruction with marginal edges and first and second door skins helpingto define an interior door cavity, a polymeric shell disposed on theinterior surface of at least one of the door skins, and a rigid foamcore disposed within the interior door cavity. In certain embodiments,the polymeric shell is the cured product of a curable mixture. Thecurable mixture can include the following components: a curable resin, aco-curable monomer and a fibrous reinforcement material. The rigid foamcore can be a rigid foamed cementitious core and more particularly afoamed cement core. Alternatively, the rigid foam core can be comprisedof a rigid foamed polyurethane core.

[0023] Yet another embodiment of the present invention includes a doorcomprising a door shell having a generally planar construction withmarginal edges and first and second door skins helping to define aninterior door cavity, a web disposed within the interior door cavity andoffset towards one of the door skins, and a rigid foamed polyurethanecore disposed within the interior door cavity and cooperating with theweb. In certain embodiments, the mat can include openings, for example,a web. The door shell can include a door frame having first and secondrails and first and second stiles. The web can be comprised of expandedmetal mesh that includes apertures having a first dimension longer thana second dimension. In one embodiment, the first dimension issubstantially parallel to the first and second stiles. The rigid foamedpolyurethane core can be comprised of the cured polyurethane foam and insome cases, can have a density of at least about 2.0 lbs/ft³.

[0024] Another embodiment of the present invention includes a doorcomprised of a door shell having a generally planar construction withmarginal edges and interior and exterior door skins helping to define aninterior door cavity, a web means for preventing access to the interiordoor skin from the exterior door skin, and a rigid foamed cementitiouscore extending between and connecting portions of the interior andexterior door skins. The web means can be disposed within the interiordoor cavity. In certain embodiments, the rigid foamed cementitious coreextends between and connects substantial portions of the skins. Therigid foamed cementitious core can be comprised of a rigid foamed cementcore. The rigid foamed cementitious core means can provide the followingattributes: the prevention of the passage of fire for at least about 20minutes using test method ASTM E2074-00 or at least about 30 minutesusing test method BSI 476/22, sound transmission coefficient rating ofat least about 27 using test method ASTM E-413, and/or a compressivestrength of at least about 210 kPa. In other embodiments, the rigidfoamed cementitious core prevents the passage of fire for at least 45minutes using test method ASTM E2074-00 or at least about 60 minutesusing test method BSI 476/22.

[0025] These and other aspects and embodiments of the present inventionwill become more apparent, clearly understood and appreciated from areading of the specification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The features of the present invention which are believed to benovel are set forth with particularity in the appended claims. Thepresent invention, both as to its organization and manner of operation,together with further objects and advantages thereof, may best beunderstood with reference to the following description, taken inconnection with the accompanying drawings:

[0027]FIG. 1A is a front elevational view of a security door accordingto an embodiment of the present invention;

[0028]FIG. 1B depicts an exploded view of a portion of expanded metalmesh in accordance with an embodiment of the present invention;

[0029]FIG. 2 depicts an exploded perspective view of a web connected tothe interior stile surfaces of a security door according to anembodiment of the present invention;

[0030]FIG. 3 depicts an exploded perspective view of a shelf machinedinto the frame edge of a security door according to another embodimentof the present invention;

[0031]FIG. 4 depicts an exploded perspective view of frame edgessuitable for the machining of a shelf;

[0032]FIG. 5 depicts a flowchart of a preferred method for mixingingredients to obtain a foamed cement slurry in accordance with anembodiment of the present invention;

[0033]FIG. 6 illustrates an apparatus in accordance with an embodimentof the present invention for filling interior door cavities with foamedcement slurry and curing the foamed cement slurry to produce agas-entrained cementitious core;

[0034]FIG. 7 depicts a cross-section of a platen which includes a tubefor conveying a heat exchanging liquid in accordance with an embodimentof the present invention; and

[0035]FIG. 8 depicts an overhead view of a schematic plant layout to beused in a system for producing doors in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] As required, detailed embodiments of the present invention aredisclosed herein. However, it is to be understood that the disclosedembodiments are merely exemplary of the invention that may be embodiedin various and alternative forms. The figures are not necessarily toscale, and some features may be exaggerated or minimized to show detailsof particular components. Therefore, specific structural and functionaldetails disclosed herein are not to be interpreted as limiting, butmerely as a representative basis for the claims and/or as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

[0037] Aspects of the present invention will now be described in detailwith reference being made to the accompanying drawings. According to theembodiment illustrated in FIG. 1A, door 10 is a hinged entry way door.It is understood that door 10 refers to, but is not limited to, hingedpatio doors, sliding patio doors, hinged interior doors,impact-resistant doors suitable for meeting high wind velocity buildingcodes, and general commercial grade doors. Door 10 can also be fittedwith a translucent panel, i.e. a doorlite assembly or side lightassembly. For example, an opening can be cut in door 10 to accept aninserted doorlite assembly. Alternatively, door 10 can be fitted with aframe assembly for accepting the translucent panel 12.

[0038] Door 10 can have many different sizes, shapes, and uses. Incertain embodiments, door 10 can have a thickness of between about 0.5inches and about 3 inches. In other embodiments, door 10 can have athickness of between about 1.25 inches and about 1.85 inches. In certainembodiments, door 10 can have a height of between about 48 inches andabout 96 inches. In other embodiments, door 10 can have a height ofbetween about 74 inches and about 96 inches. In certain embodiments,door 10 can have a width of between about 8 inches and about 48 inches.In other embodiments, door 10 can have a width of between about 10inches and about 44 inches. In yet other embodiments, door 10 can have awidth of between about 30 inches and about 42 inches.

[0039] As shown in FIG. 1A, door shell 14 includes first door skin 16,second door skin 18 and door frame 20. It should be understood that onedoor skin can be an exterior door skin and the other door skin can be aninterior door skin based on how the door is hinged to the entry way. Inthe illustrated embodiment, the exterior door skin typically faces anoutside environment and the interior door skin faces an insideenvironment (i.e. the inside of a house containing the entry way forhinging the door). Door shell 14 helps to define interior door cavity22. Door shell 14 can be comprised of a blow-molded material, forexample, a pre-pigmented plastic, a thermoformed material or atwin-sheet thermoformed material. The door skins include an exteriorside and an interior side. The interior sides face interior door cavity22 and the exterior sides face away from interior door cavity 22.Suitable materials for the door skins include reinforced or unreinforcedmatrix materials of thermoset (i.e. thermoset materials), steel,aluminum, thermoplastic, ceramic, wood or combinations thereof,preferably thermoset materials, and most preferably fiberglassreinforced thermoset materials. In certain embodiments, the door frameis constructed with materials that are machinable with common buildingtools.

[0040] Door frame 20 includes a first stile 24 and a second stile 26.Stiles 24 and 26 are parallel to one another. Stiles 24 and 26 arepositioned in a perpendicular relationship to first rail 28 and secondrail 30. Second rail 30 is parallel to and spaced apart from first rail28. First rail 28 and second rail 30 extend between and connect tostiles 24 and 26. Stiles 24 and 26 and rails 28 and 30 can beconstructed of laminated or unlaminated wood. Stiles 24 and 26 can alsobe a hollow channel of pultruded or extruded reinforced plastic, a metalhollow channel, a partially or totally metal reinforced channel made ofa material other than metal, or a compressed mineral stile. According toFIG. 1A, door frame 20 has a rectangular geometric configuration.However, it is understood that door frame 20 can be arranged in avariety of geometric configurations depending upon the desiredapplication. For example, door frame can have a radiused or arched toptypical of “mission style” architecture.

[0041] First hinge insert 32, second hinge insert 34 and lock insert 36can be inserted into the door shell 14. Hinge inserts 32 and 34 can befastened to second stile 26, adhered to either or both first door skin16 or second door skin 20, or inserted into pre-defined spaces in eitheror both first door skin 16 or second door skin 18. Lock insert 36 can befastened to first stile 24, adhered to either or both first door skin 16or second door skin 18, or inserted into pre-defined spaces in both oreither door skins 16 and/or 18. First hinge plate 38 and second hingeplate 40 can be secured to first hinge insert 32 and second hinge insert34 by using a screw, nail, or similar fastener. Lock apparatus 42 can besecured to lock insert 38 by using a screw, nail or similar fastener.

[0042] Referring to FIG. 1A, web 44 can be disposed within interior doorcavity 22. In certain embodiments, the material used for web 44 providesimpact resistance and can prevent access to the interior door skin fromthe exterior side of the door skin by using, for example, sharp cuttingtools. Portions of web 44 can be removed so that web 44 does notinterfere with hinge inserts 32 and 34 and lock insert 36. Also, itshould be understood that a plurality of layers of webs can be used forimpact and intrusion resistance requirements.

[0043] Examples of web materials that provide impact resistance include,but are not limited to, plastic web materials, such as rubber-basedplastics, soft durometer plastics, and polyolefin web materials. Anexample of a suitable soft durometer plastic can be a vinyl rubber mat.In certain embodiments, vinyl rubber mat sheets with a thickness ofabout 0.25 inches can be used. Suitable polyolefin web materials includethose typically used as snow fences and/or construction barriers. Incertain embodiments, these types of webs with a thickness of about 0.1inches are used. It should be understood that web materials suitable forimpact resistance need not be primarily planar sheets and can havesignificant thickness (in the range of about 0.01 inches to about 0.75inches), for example dimensional monofilament materials such asCOLORBOND available from BHP Steel of Australia.

[0044] Examples of web materials that are suitable for use and that alsoprovide impact resistance and prevention of access to the interior doorskin from the exterior door skin using, for example, sharp cutting toolsinclude, but are not limited to, metal screen, polymer woven screen,expanded metal mesh, and wire form.

[0045] In other embodiments, a mat can be disposed within interior doorcavity 22 and is generally rectangular in shape. It should be understoodthat a mat may or may not have openings. Examples of materials for mats,can include, but are not limited to, a plastic chamber with inflatinggas, a ballistic resistant material, gypsum core, a solid metal mat, anda solid polymeric sheet. In certain embodiments, the mat can allow thefoamed cement slurry to be poured on both sides of the mat.

[0046]FIG. 1B illustrates an exploded portion of expanded metal mesh inaccordance with an embodiment of the present invention. The expandedmetal mesh is preferably comprised of a network of apertures 46, i.e.openings, having a first dimension 48 and a second dimension 50. Incertain embodiments, the ratio of the first dimension to the seconddimension, otherwise referred to as the aspect ratio, can be greaterthan about 1.1. In other embodiments, the first dimension can be about0.2 inches to about 1.5 inches and the second dimension can be about0.18 inches to about 1.35 inches. However, it should be understood thatthe first and second dimensions can be greater than about 1.5 inches andabout 1.35 inches, respectively, provided that the apertures are smallenough to not allow penetration by a hand of an intruder and/or animpacting object through the expanded metal mesh. It should also beunderstood that the first and second dimensions can be less than about0.2 inches and about 0.18 inches, respectively, provided that theapertures are large enough to allow a rigid foam to pass through theexpanded metal mesh during pouring (this step is described in greaterdetail below).

[0047] In certain embodiments, the thickness of the expanded metal meshcan be about 0.3 inches to about 2.0 inches. In other embodiments, thethickness can be 0.04 inches. Suitable thicknesses can provide arelatively inexpensive web material while providing the advantages ofimpact resistance and entry prevention. In certain embodiments, web 44is comprised of expanded metal mesh which can be disposed withininterior door cavity 22 for maximum tensile strength by orienting theexpanded metal mesh so that the first dimension is parallel to rails 28and 30.

[0048]FIG. 2 depicts an embodiment for disposing web 44 within interiordoor cavity 22. The lengthwise edges of web 44 can be bent to form firstbent portion 52 and second bent portion 54. Bent portions 52 and 54 canhave a uniform width of about 0.5 inches and about 1.0 inches. Incertain embodiments, bent portions 52 and 54 can be substantiallyperpendicular to the adjoining flat portion 56 of web 44 and bent in thesame direction so that they face each other. Bent portions 52 and 54 canbe secured to at least a portion of first stile surface 58 and secondstile In certain embodiments, flat portion 56 is closer to the exteriordoor skin than the interior door skin so that the added layer ofprotection (i.e. web 44) is closer to the exterior door skin which isvulnerable to attack.

[0049]FIGS. 3 and 4 depict another embodiment for disposing web 44within interior door cavity 22. In the depicted embodiment, shelf 62 ismachined, or otherwise formed, into all four sides of the frame edge.However, it should also be understood that shelf 62 may be machined intoa portion the frame edge contained on stiles 24 or 26 or contained onrails 28 and 30. According to FIGS. 3 and 4, shelf 62 is machined intofirst frame edge 64 which is adjacent to first door skin 16 uponassembly of door 10. It should be understood that shelf 62 can also bemachined into second frame edge 66 which is adjacent to second door skin18 upon assembly of door 10.

[0050] Shelf 62 is comprised of first shelf surface 68 and second shelfsurface 70. In certain embodiments, first shelf surface 68 issubstantially parallel to door skins 16 and 18 and second shelf surface70 is substantially perpendicular to door skins 16 and 18. In certainembodiments, the width of first shelf surface 68 can be at most abouthalf the width of stiles 24 and 26. In certain embodiments, the width ofsecond shelf surface 70 can be in the range of about the thickness ofweb 44 and about half the thickness of door 10.

[0051] In certain embodiments, the width of second shelf surface 70 isabout the thickness of web 44 and shelf 62 is machined into the frameedge which is adjacent to the exterior door skin upon assembly. Incertain embodiments, the door assembly provides the added layer ofprotection, i.e. web 44, adjacent to the exterior door skin which isvulnerable to attack.

[0052] In certain embodiments, the length and width of web 44 is greaterthan the length and width of interior door cavity such that the edges ofweb 44 lay flat upon first shelf surface 64 and can be secured to firstshelf surface 68 with staples, brads, nails, screws or other fasteners.

[0053] According to another method of disposing web 44 within theinterior door cavity 22, web 44 can be placed within interior doorcavity 22 without being secured to door frame 20. According to thisembodiment, web 44 is secured within interior door cavity 22 through thefoaming process, described in more detail below.

[0054] In certain embodiments, door skins 16 and 18 are secured to doorframe 20 after web 44 is secured to door frame 20. In these embodimentsas well as others, door skins 16 and 18 are secured to door frame 20with an adhesive. Suitable adhesives include, but are not limited to,latex acrylic, hot melt urethane, epoxy, pressure sensitive adhesives,and radiation cured adhesives. It is understood that door skins 16 and18 can include interlocking edges that function to secure door skins 16and 18 to door frame 20. Alternatively, an interlocking skin can be usedinstead of first door skin 16 and second door skin 18. The interlockingdoor skin fits over the door frame 18 and the edges of the interlockingdoor skin mate together, for example, with snap-fits.

[0055] In certain embodiments of the present invention, a rigid foamcore disposed within the interior door cavity is then provided, asdescribed in greater detail below. In certain embodiments, the rigidfoam core prevents the passage of fire for at least about 20 minutesusing test method ASTM or at least about 30 minutes using test methodBSI 476/22. In other embodiments, the rigid foamed cementitious coreprevents the passage of fire for at least 45 minutes using test methodASTM E2074-00 or at least about 60 minutes using test method BSI 476/22.In certain embodiments, the rigid foam core provides a soundtransmission coefficient rating of at least about 27 using test methodASTM E-413. In certain embodiments, the rigid foam core can have acompressive strength of at least about 210 kPa (about 30 lbf/in²).Examples of foams that provide rigid foam cores with the fire and soundratings disclosed above include polyurethane foams having a minimumdensity of at least about 2.0 lb/ft³ and those formed from gas-entrainedcementitious materials. In certain embodiments, the gas-entrainedcementitious material can be a controlled low strength cementitiousmaterial, or more specifically an air-modified controlled low strengthcementitious material, or most specifically a foamed cement slurry.

[0056] Gas-entrained cementitious materials refer to inorganic materialsor mixtures of inorganic materials which sets and develops strength by achemical reaction with water by formation of hydrates, and whichentrains more than about 5 volume % gas, preferably between about 10 andabout 80 volume %, more preferably between about 30 and about 60 volume%, and most preferably between about 40 and about 55 volume %. It isunderstood that the gas can come from a variety of sources including,but not limited to direct gas injection, microspheres containing gases,porous particles containing gases, and in-situ chemical reactions orchanges in the state of matter. It is further understood that materialsentrained may not always be in the gaseous phase, particularly whenenvironmental temperatures to which the article is exposed changesignificantly. It is further understood that the gases may migratethrough time and be replaced by other gases or liquids.

[0057] Controlled low strength cementitious material (CLSM), a subset ofgas-entrained cementitious materials, refers to a generic term forflowable cementitious materials having a self-compacting property and acompressive strength of less than about 1,200 lbf/in² (8.27 Mpa) and anunconfined ultimate compressive strength of between about 30 lbf/in² andabout 500 lbf/in². In other embodiments, an unconfined compressivestrength of between about 50 lbf/in² and about 250 lbf/in². CLSMs arealso commonly referred to as flowable fill, flow fill, or controlleddensity fill.

[0058] Air-modified controlled low strength cementitious materials canbe referred to as a CLSM which has entrained in it more than 5 volume %air. In certain embodiments, the entrainment can be between about 10 toabout 80 volume % air. In other embodiments, the entrainment can bebetween about 30 to about 60 volume % air. In yet other embodiments, theentrainment can be about 40 to about 55 volume % air.

[0059] Foamed cement slurries can refer to a type of air-modifiedcontrolled low strength cementitious material in which the cementitiousmaterial is any type of hydraulic cement, and in some embodimentsPortland cement, in which air or other gases are entrained at more thanabout 5 volume % air or other gas. In certain embodiments, theentrainment can be between about 10 to about 80 volume % air or othergas. In other embodiments, the entrainment can be between about 30 toabout 60 volume % air or other gas. In yet other embodiments, theentrainment can be between about 40 to about 55 volume % air or othergas. Portland cement can be defined in ASTM C-150 and is a variety ofblended hydraulic cement as defined in ASTM C-595.

[0060] In certain embodiments, foamed cement slurries can be utilized toproduce gas-entrained cementitious cores by transferring the foamedcement slurry into the interior door cavity 22 and curing the slurries.It should be understood that the curing occurs through a hydration,otherwise referred to as a water-based reaction. The foamed cementslurry can be prepared by mixing a combination of ingredients. FIG. 5depicts a flowchart of a method for mixing ingredients to obtain afoamed cement slurry in accordance with the present invention. Accordingto FIG. 5, cement 72 and water 74 are mixed in a high speed mixer 76 toproduce cement slurry 78. As depicted in block 80, a brewing step isutilized to produce foaming solution 82. Typically, the brewing stepincludes mixing air and water with a foaming agent to produce a foamingsolution with entrained air. In one embodiment, cement slurry 78,foaming solution 82, and expanded polystyrene (EPS) beads 84 areintroduced into gentle mixer 86 and mixed to produce foamed cementslurry 88. Optionally, fiber spools 90 can be fed into chopper 92 toproduce reinforcement fibers 96, which can be introduced into gentlemixer 86 along with the other ingredients. Once mixed, the foamed cementslurry can be transferred into interior door cavity 22.

[0061] In certain embodiments, the water to cement ratio in the foamedcement slurry is greater than about 38 parts water to about 100 partscement by weight in order to provide strength to the resulting doormember. Optional additives, such as water reducers, settingaccelerators, superplasticizers, reinforcement fibers, and expandedpolystyrene beads, can be added to the foamed cement slurry to enhanceproperties, such as flow rate, curing rate, weight, or rigidity. Itshould be understood that reinforcing fibers refer to a fiber or abundle of fibers having an aspect ratio greater than about 4, whichresults in one or more increased mechanical properties when present.

[0062] Water reducers, in general, improve the workability of cementslurries and reduce the amount of mixing water for a given workability.Typically this is about 5-15% reduction in water usage. Water reducerscan be frequently drawn from the groups consisting of condensednaphthalene sulfonic acids, salts of lignosulfonic acids, salts ofhydroxycarboxylic acids, carbohydrates and blends thereof.Superplasticizers, also known as superfluidizers, super water reducers,and high range water reducers, are a class of water reducers capable ofreducing the water usage by at least about 30%. While not being bound toany one theory, it is believed that superplasticizers break down thelarge irregular agglomerates of cement particles by virtue ofdeflocculation due to adsorption and electrostatic repulsion, as well assome steric effects. Superplasticizers are typically drawn from a groupconsisting of sulfonated melamine-formaldehyde condensates, sulfonatednaphthalene-formaldehyde condensates, modified lignosulfonates, sulfonicacid esters, polyacrylates, polystyrene sulfonates, and blends thereof.

[0063] Many cements that are suitable for use in the present inventioncontain additives. These additives can include cementitious andpozzolanic additives. Cementitious additives refer to an inorganicmaterial or mixture of inorganic materials which forms or assists toform cementitious materials which develops strength by chemical reactionwith water by formation of hydrates. Cementitious additives aregenerally rich in silica and alumina. According to ASTM C-539-94,pozzolanic additives refer to siliceous or alumino-siliceous materialwhich in itself possesses little or no cementitious value, but whichwhen in finely divided form and in the presence of moisture willchemically react with alkali and alkaline earth hydroxides at ordinarytemperatures to form or assist in forming compounds possessingcementitious properties. Examples of pozzolanic additives can includeClass C fly ash from burning lignite coal, Class F fly ash from burningbituminous coal, pulverized-fuel fly ash, condensed silica fume,metakaolin, rubber ash, and glass cullet. Additives found in cement areparticularly useful in increasing the mass of the resulting door member.

[0064] Insulating gases can replace entrained air to provide greaterinsulation. These gases include molecules that generally have a higheratomic mass than air. Possible examples include halocarbons andhydrohalocarbons, such as HCFC-22, HFC-134a, HFC-245fa, HFC-365mfc;noble gases, such as argon, xenon, and krypton; sulfur hexafluoride;hydrocarbons, such as pentane; and mixtures thereof.

[0065]FIG. 6 depicts an apparatus in accordance with an embodiment ofthe present invention for filling interior door cavities with foamedcement slurry and curing the foamed cement slurry to produce agas-entrained cementitious core. In the depicted embodiment, the fillingstructure is comprised of door shell bank 98, filling station 100, andheat exchanger system 102.

[0066] Door shell bank 98 is comprised of sled 104 having first andsecond sled panels 106 and 108. In certain embodiments, sled panels 106and 108 can be generally rectangular in shape and constructed fromplywood. The longer edges of generally rectangular sled panels 106 and108 can be fitted with a first and second plurality of castors 110 and112, respectively, for facilitating movement of sled 104 around anassembly floor.

[0067] In the depicted embodiment, door shell bank 98 is also comprisedof first and second reinforcement shell ends 114 and 116, first andsecond platen shell 118 and 120, a plurality of door shells 122, and atleast one platen center shell 124, which are loaded onto sled 104 inpreparation for filling the plurality of door shells 122 with the foamedcement slurry. In alternative embodiments, reinforcement can be providedby a plurality of metal reinforcement sheets of substantial thickness(between about 0.5 inches to about 2.0 inches) placed between the doorshell or by the door frame itself if made out of fabricated metal, forexample, in the case of metal fire doors. In yet other embodiments, thereinforcement can be provided by a plurality of spaced apart andreinforced open mouth cavities such that each reinforced cavity issuitable for housing at least one article shell. In certain embodiments,the loading process is comprised of orienting sled 104 such that secondsled panel 108 is substantially parallel to the assembly floor, slidingitems 114 through 124 onto second sled panel 108 in an order, and thentipping sled 104 about ninety degrees so that first sled panel 106 issubstantially parallel to the assembly floor. In certain embodiments,the order from one end to the other end of sled 104 can be thefollowing: first reinforcement shell end 114, first platen shell 118,door shell 120, platen center shell 124, door shell 120, second platenshell 122, and second reinforcement shell end 116. It is fullycontemplated that greater than two door shells can be loaded onto sled104 as long as additional platen center shells 124 are loaded in betweenthe door shells. In certain embodiments, 10-15 door shells with 11-16platen center shells 124 are loaded onto sled 104. However, it should beunderstood that this is merely exemplary of the amount doors that can bepaired in tandem with platen center shells. Other amounts can be usedbased on the amount of time necessary to set the foamed cement slurry.First rail of each door shell 120 faces upward from an assembly floorand second rail of each door shell 120 preferably sits flush againstfirst sled panel 106 after sled 104 can be tipped about ninety degrees.

[0068] In certain embodiments, reinforcement shell ends 114 and 116 aregenerally rectangular in shape with a height and length similar to doorshell 122 and can be comprised of a metal alloy sheet of substantiallyuniform thickness which is fabricated into a one-piece, hollowrectangular box with strength sufficient to resist buckling under vacuumconditions. Suitable pure metal or metal alloys for this purpose,include, but are not limited to, aluminum, stainless steel, carbonsteel, cast iron, and alloys thereof. In certain embodiments, the widthof reinforcement shell ends 114 and 116 can be in the range of about0.05 inches to about 4.0 inches. In other embodiments, the width can bein the range of about 0.625 inches to about 1.0 inches. In certainembodiments, the width can be in the range of about 0.625 inches toabout 0.75 inches.

[0069] In certain embodiments, platen shells 118, 120, and 124 can begenerally rectangular, with a height and length similar to door shell122. Such platens can be comprised of a metal sheet of substantiallyuniform thickness which is fabricated into a one-piece, hollowrectangular box with strength sufficient to resist bucking under vacuumconditions. Suitable pure metal or metal alloys for this purpose,include, but are not limited to, aluminum, stainless steel, carbonsteel, cast iron, and alloys thereof. In certain embodiments, the widthof reinforcement shell ends 114 and 116 can be in the range of about0.05 inches to about 4.0 inches. In other embodiments, the width can bein the range of about 0.625 inches to about 1.0 inches. In certainembodiments, the width can be in the range of about 0.625 inches toabout 0.75 inches.

[0070] In certain embodiments, platen shells 118, 120, and 124 canprovide heat to the foamed cement slurry encased in the surrounding doorshells in order to decrease the green-strength curing time, as describedin greater detail below. The heat decreases the time necessary for thecement in the foamed cement slurry to form a structurally stable cellwall around entrained gas and/or air bubbles. In certain embodiments,the interior cavity of platens 118, 120, and 124 house a tube generallyfollowing a serpentine path for conveying a heat exchanging liquid. Itis fully understood that the other path configurations can be used aslong as they can be used to deliver heat to a substantial portion of theplaten surface.

[0071] For example, FIG. 7 depicts a cross-section of platen 118 aboutplane 7-7 which includes tube 126 for conveying a heat exchangingliquid. In the depicted embodiment, tube 126 enters the interior shellcavity of platen shell 118 through opening 128, extends through agenerally serpentine path and exits through opening 130. In certainembodiments, the heat exchanging liquid can be introduced into a heaterfor heating the liquid to a temperature in the range of about 1° C. toabout 70° C. above ambient, more particularly about 10° C. to about 40°C., and most particularly about 20° C. to about 35° C. In certainembodiments, the heat exchanging liquid can enter the interior cavity ofthe platen in tube 126 through opening 128. As the heat exchangingliquid flows through tube 126 towards opening 130, it loses heat to therelatively cooler adjacent liquid cement slurry. This heat exchange aidsin decreasing the green strength curing time. The cooled heat exchangingliquid exits the interior door cavity in tube 126 through opening 130which feeds into a return line. Preferably, the heat exchanging liquidis circulated for further use. Examples of suitable heat exchangingliquids include, but are not limited to, water, oil, or THERMOL. Incertain embodiments, the return line is connected to the heater througha recirculating line for recycling the heat exchanging liquid to provideenergy savings.

[0072] According to the embodiment as shown in FIG. 6, filling station132 is comprised of filling nozzle 134, vacuum lines 136, and platform138. Nozzle 134 can deliver foamed cement slurry into interior doorcavity 22. The foamed cement slurry can be transferred into interiordoor cavity incrementally, using between one and five increments. Incertain embodiments, one to three increments can be used. In otherembodiments, one increment can be used. In certain embodiments, nozzle134 can be part of a gravity feed system for transferring foamed cementslurry from gentle mixer 86 into interior door cavity 22. In theseembodiments, the contents of gentle mixer 86 can be poured under theforce of gravity into a hopper. The hopper can be mechanicallypositioned over interior door cavity 22 and foamed cement slurry flowvia a pump from the hopper through nozzle 134 into interior door cavity22. This system can reduce costs by limiting the destruction of bubblespassing through the compressive phase of the pump. In certainembodiments, platform 138 is positioned over loaded door steel bank 98and is in the vicinity of filling nozzle 134 such that an operator canmove the filling nozzle between door shells. In certain embodiments, atleast one vacuum line 136 can be attached to a shell edge of at leastone platen shell 118 for providing suction between the door skin and areinforcement shell surface so that the door shell retains itspre-curing shape during curing.

[0073]FIG. 8 depicts an overhead view of a schematic plant layout to beused in a system for producing doors in accordance with an embodiment ofthe present invention. In the depicted embodiment, the system caninclude a plurality of door shell banks 140 which are positioned belowat least one platform 142 having a vacuum and slurry source forsupplying a vacuum to reinforcement shells of door shell banks 140 anddelivering the gas-cementitious material to the interior cavity of doorshells, respectively. In certain embodiments, the filled doors can bemoved on door shell banks 140 to a curing area 144, which can be acuring room, in order to green-strength cure the filled door shells.After curing, the doors can proceed to trim line 146 and pallets 148.

[0074] In certain embodiments, an adhesive can be applied to theinterior surface of each door skin of each door before being loaded ontosled 104. The adhesive helps to adhere the foamed cement slurry to theinterior surfaces during the curing process. Examples of suitableadhesives include, but are not limited to, latex adhesive, epoxy, hotmelt urethane, radiation cured adhesives, and mixtures thereof. Theadhesive can reduce the time necessary to achieve green-strength, i.e.when the door can be removed from the fixture without damage, forexample, inducing cracking, and increases the strength of the door uponfinal setting. It should be understood that in certain embodiments thefoamed cement slurry can reach this green-strength after at leastpartially curing the foamed cement slurry and without the use of anadhesive.

[0075] According to another embodiment of the present invention, acurable mixture is applied to the interior surface of at least one doorskin and the interior surface of the door frame. The curable mixturecures to form a polymeric shell which can increase the security ratingand/or the strength of the door. In certain embodiments, the curablemixture can be a viscous liquid when applied and dries upon curing toform a curable shell. The curable mixture can be applied to form thepolymeric shell in a range of at least about 0.5 inches when dry to thefull width of the interior door frame and within about 2.0 inches of theinterior door frame corners to the full length of the interior doorframe.

[0076] In certain embodiments, the curable mixture can be comprised of acurable resin, a co-curable monomer, a filler material, and a fibrousreinforcement material. Sufficient filler material can be added toprevent shrinkage of the curable shell. The amount of filler materialnecessary varies according to the amount of curable resin used in thecurable mixture. In certain embodiments, the filler material cancomprise between about 30% to about 80% by weight of the curablemixture. Unless otherwise stated, all percentages disclosed are byweight based on the total weight of the curable mixture. In otherembodiments, about 50% to about 75% filler material can be used. In yetother embodiments, about 60% to about 74% filler material can be used.The fibrous reinforcement material can be selected from choppedfiberglass, woven fiberglass mat, nonwoven fiberglass mat, needledfiberglass mat, aramid fiber mat, carbon fiber mat, nylon screen,rubber-coated textiles, plastic laminated fibers, and combinationsthereof. In certain embodiments, the fibrous reinforcement material cancomprise about 10% to about 40% of the curable mixture. In otherembodiments, the fibrous reinforcement material can comprise about 15%to about 35% of the curable mixture. In yet other embodiments, thefibrous reinforcement material can comprise about 17% to about 30% ofthe curable mixture.

[0077] While embodiments of the invention have been illustrated anddescribed, it is not intended that these embodiments illustrate anddescribe all possible forms of the invention. Rather, the words used inthe specification are words of description rather than limitation, andit is understood that various changes may be made without departing fromthe spirit and scope of the invention.

What is claimed is:
 1. A door comprising: a door shell having agenerally planar construction with marginal edges and first and seconddoor skins helping to define an interior door cavity; a mat within theinterior door cavity; and a rigid foamed cementitious core within theinterior door cavity.
 2. The door of claim 1 wherein the mat includesopenings.
 3. The door of claim 2 wherein the mat is comprised of a web.4. The door of claim 1 wherein the mat is comprised of a substantiallyrectangular plastic bladder filled with gas.
 5. The door of claim 1wherein the mat is comprised of a ballastic resistant material.
 6. Thedoor of claim 1 wherein the door shell is comprised of a blow-moldingmaterial.
 7. The door of claim 6 wherein the blow-molding material iscomprised of a pre-pigmented plastic.
 8. The door of claim 6 wherein theblow-molding material is comprised of a thermoformed material.
 9. Thedoor of claim 8 wherein the thermoformed material is comprised of atwin-sheet thermoformed material.
 10. The door of claim 1 furthercomprising an adhesive layer partially coating the internal surface ofat least one door skin for at least partially adhering the rigid foamedcementitious core to the at least one door skin.
 11. The door of claim10 wherein the adhesive is selected from the group consisting of latexacrylic, hot melt urethane, epoxy, pressure sensitive adhesives, andradiation cured adhesives.
 12. The door of claim 1 wherein the rigidfoamed cementitious core cooperates with the mat.
 13. The door of claim1 wherein the rigid foamed cementitious core is comprised of a foamedcement core.
 14. The door of claim 1 wherein the door skins arecomprised of fiberglass.
 15. The door of claim 1 wherein the door skinsare comprised of a thermoplastic material.
 16. The door of claim 3wherein the rigid foamed cementitious core is disposed between the firstand second door skins and on at least one side of the web.
 17. The doorof claim 3 wherein the rigid foamed cementitious core is disposedbetween the first and second door skins and on both sides of the web.18. The door of claim 3 wherein the web is offset towards one of thedoor skins.
 19. The door of claim 3 wherein the web is substantiallycentered in the interior door cavity.
 20. The door of claim 3 whereinthe web is closer to one of the door skins than to the other door skin.21. The door of claim 3 wherein the web is comprised of a metal screen.22. The door of claim 3 wherein the web is comprised of a polymer wovensheet.
 23. The door of claim 1 wherein the rigid foamed cementitiouscore prevents the passage of fire for at least about 20 minutes usingtest method ASTM E 2074-00 or at least about 30 minutes using testmethod BSI 476/22.
 24. The door of claim 23 wherein the rigid foamedcementitious core prevents the passage of fire for at least about 45minutes using test method ASTM E2074-00 or at least about 60 minutesusing test method BSI 476/22.
 25. The door of claim 1 wherein the foamedcementitious core provides a sound transmission coefficient rating of atleast about 27 using test method ASTM E-413.
 26. The door of claim 1wherein the foamed cementitious core has a compressive strength of atleast about 210 kPa.
 27. The door of claim 3 wherein at least two websare disposed within the interior door cavity.
 28. The door of claim 3wherein the web is comprised of an expanded metal mesh.
 29. The door ofclaim 28 wherein the door shell includes a door frame having first andsecond rails and first and second stiles.
 30. The door of claim 29wherein the expanded metal mesh includes apertures having a firstdimension longer than a second dimension and the first dimension beingsubstantially parallel to the first and second stiles.
 31. A doorcomprising: a door frame and at least one door skin being connected andhelping to define an interior door cavity; a mat within the interiordoor cavity; and a rigid foamed cementitious core within the interiordoor cavity.
 32. A method of constructing a door comprising: providing adoor shell having a generally planar construction with marginal edgesand first and second door skins helping to define an interior doorcavity; disposing a mat within the interior door cavity; and disposing arigid foamed cementitious core within the interior door cavity, therigid foamed cementitious core cooperating with the web.
 33. The methodof claim 32 wherein the mat includes openings.
 34. The method of claim33 wherein the mat is comprised of a web.
 35. The method of claim 34wherein the web is disposed within the interior door cavity prior todisposing the rigid foamed cementitious core within the interior doorcavity.
 36. The method of claim 34 wherein the web is disposed offsettowards one of the door skins.
 37. The method of claim 34 wherein theweb is disposed substantially centered in the interior door cavity. 38.The method of claim 34 further comprising securing the web to at leastone of the door skins.
 39. The method of claim 34 further comprisingsecuring the web to the marginal edges of the door shell.
 40. The methodof claim 34 further comprising forming a shelf into the marginal edgesof the door shell.
 41. The method of claim 40 wherein the forming stepis comprised of removing a portion of the marginal edges such that afirst and second shelf surface is formed into the marginal edges. 42.The method of claim 41 wherein the first shelf surface is substantiallyparallel to the first and second doors skins and the second shelfsurface is substantially perpendicular to the first and second doorskins.
 43. The method of claim 42 further comprising securing at least aportion of the web to at least a portion of the first shelf surface. 44.The method of claim 43 wherein the second shelf surface is offsettowards one of the door skins.
 45. The method of claim 44 wherein thesecond shelf surface is substantially centered between the first andsecond door skins.
 46. A door comprising: a door shell having agenerally planar construction with marginal edges and first and seconddoor skins helping to define an interior door cavity; a polymeric shelldisposed on the interior surface of at least one of the door skins; anda rigid foam core disposed within the interior door cavity.
 47. The doorof claim 46 wherein the polymeric shell is the cured product of acurable mixture.
 48. The door of claim 47 wherein the curable mixtureincludes a curable resin and a co-curable monomer.
 49. The door of claim48 wherein the curable mixture further includes a filler material. 50.The door of claim 49 wherein the curable mixture further includes afibrous reinforcement material.
 51. The door of claim 46 wherein therigid foam core is comprised of a rigid foamed cementitious core. 52.The door of claim 51 wherein the rigid foamed cementitious core iscomprised of a foamed cement core.
 53. The door of claim 46 wherein therigid foam core is comprised of a rigid foamed polyurethane core.
 54. Adoor comprising: a door shell having a generally planar constructionwith marginal edges and first and second door skins helping to define aninterior door cavity; a mat disposed within the interior door cavity andoffset towards one of the door skins; and a rigid foamed polyurethanecore disposed within the interior door cavity and cooperating with themat.
 55. The door of claim 54 wherein the mat includes openings.
 56. Thedoor of claim 55 wherein the mat is comprised of a web.
 57. The door ofclaim 56 wherein the web is comprised of expanded metal mesh.
 58. Thedoor of claim 57 wherein the door shell includes a door frame havingfirst and second rails and first and second stiles.
 59. The door ofclaim 58 wherein the expanded metal mesh includes apertures having afirst dimension longer than a second dimension and the first dimensionbeing substantially parallel to the first and second stiles.
 60. Thedoor of claim 56 wherein the rigid foamed polyurethane core is comprisedof the cured product of a polyurethane foam.
 61. The door of claim 60wherein the polyurethane foam has a density of at least about 2.0lb/ft³.
 62. A door comprising: a door shell having a generally planarconstruction with marginal edges and interior and exterior door skinshelping to define an interior door cavity; a web means for preventingaccess to the interior door skin from the exterior door skin, the webmeans being within the interior door cavity; and a rigid foamedcementitious core extending between and connecting at least portions ofthe interior and exterior door skins.
 63. The door of claim 62 whereinthe rigid foamed cementitious core extends between and connectssubstantial portions of the skins.
 64. The door of claim 62 wherein therigid foamed cementitious core is comprised of a rigid foamed cementcore.
 65. The door of claim 62 wherein the rigid foamed cementitiouscore prevents the passage of fire for at least about 20 minutes usingtest method ASTM E 2074-00 or at least about 30 minutes using testmethod BSI 476/22.
 66. The door of claim 65 wherein the rigid foamedcementitious core prevents the passage of fire fore at least 45 minutesusing test method ASTM E2074-00 or at least about 60 minutes using testmethod BSI 476/22.
 67. The door of claim 62 wherein the foamedcementitious core provides a sound transmission coefficient rating of atleast about 27 using test method ASTM E-413.
 68. The door of claim 62wherein the foamed cementitious core has a compressive strength of atleast about 210 kPa.